Washington (CNN)Five of the seven Navy sailors who died aboard the guided-missile destroyer USS Fitzgerald when it collided with a cargo ship off the east coast of Japan may have been almost instantly "incapacitated" and died quickly, according to a preliminary Navy analysis, a defense official told CNN.

That assessment is based on an examination of the point of impact and the berths in which the sailors were likely sleeping.

The two ships collided on the Fitzgerald's starboard side directly next to the berthing area, where sailors sleep. The impact ripped the Fitzgerald open and caused water to pour in.

The official also noted the Navy is trying to corroborate accounts which suggest that the two sailors who weren't almost instantly "incapacitated" attempted to help the other five escape the incoming water.

"But at some point the ship somehow lost communication," with the two sailors and they also perished, according to the official. All seven were found dead in the flooded area.

It also appears that the collision caused part of the berthing compartment to collapse inward, making it difficult for survivors to get out.
The official said It may never be known if the order to close the watertight hatch to the berthing area came while the two men were still alive.
The formal investigation will determine who gave that order, but the initial sense is the decision was necessary because water had not only flooded the berthing area but was flowing into other locations including a deck below.
The official emphasized that the Navy will wait for all the investigations to be completed before coming to any conclusions about the actions of the crew and decisions over citations for heroism or potential disciplinary action.
The official also strongly emphasized that no judgments are being made about the timing of the decision to shut the watertight hatch. It is also not clear if those on the bridge called the commanding officer as the crisis unfolded.

The collision occurred very close to the cabin of Cmdr. Bryce Benson, and he was briefly unable to get out. The crew helped him to the bridge, but he was so badly injured that he had to be medevaced off the ship and the second in command took over.
The US Navy, the US Coast Guard, and Japanese naval and maritime authorities are all conducting investigations.
An early assessment suggests the container ship might have been on some type of autopilot system at the time of the collision, the official said.
However, that does not explain how and why the crew of the Fitzgerald did not see the other ship coming, or why they were unable to maneuver away from it, the official said.
Initial reports suggest that the collision occurred at 1:30 a.m., but the container ship crew did not automatically realize it had happened. The container ship turned back, and it appears the collision was then formally reported around 2:20 a.m.

To help determine what happened, investigators will download radar data from the ship's Aegis weapons system, which records routine details on position, course, speed and any nearby ships or aircraft. Navigation and radar data will also be gathered from the cargo ship.
Another factor being examined is the impact of the destruction of the Fitzgerald's communications gear on the ability of the crew to call back to shore to inform commanders they needed help.
Preliminary analysis indicates the collision occurred where the ship's communication nodes are housed and the official said the crew had to resort to using satellite based cell phones to communicate both on board and back to shore.